platinum was substituted for the brass. The English pound weight is still this platinum standard pound. Copies of it, also of platinum, are kept in the United States (Washington) and in other countries.

The abbreviation "lb.," for "pound," comes from the Latin libra, or scales. The word "ounce" is probably from unus, "one," and was originally applied to of a pound, as it still is in "Troy" weight. In the form "inch" it was also applied to is of a foot. The ton probably received its name from the "tun," a large cask that held about 2,000 pounds of water.

14. Metric Units of Weight.In the metric system the common weight units are the gram and kilogram (1000 grams). A liter of pure water at 4° C. (cf. § 87) weighs one kilogram. This is abbreviated to "kilo" or to "kg." The international standard kilogram is a piece of platinum, as is the English standard

pound. Forty of these were constructed in Paris, and two of them are in the Bureau of Standards, at Washington (Fig. 12).

One cubic centimeter of water, that is, 1,000 of a liter, weighs one gram.

Subdivisions of the gram, like those of the meter, are formed from the prefixes "milli," "centi," and "deci."

Two advantages which the metric system has over the English system are:

(1) It is a decimal system.

(2) It is already in use in practically all of Europe, and in Latin America.

Just as we can gather together "one dollar, four dimes, and three cents" into the expression "$1.43," so we can write "two grams, five decigrams, three centigrams, and one milligram" as "2.531 g." A weight consisting of several English units, such as two pounds, six ounces, and fifteen grains, cannot be expressed in pounds without much calculation.

15. Bureau of Standards. Since it is important that all apparatus used for measuring shall be correct, several governments have established "Bureaus of Standards,' to which such apparatus may be sent for the purpose of comparing it with the standard apparatus of the government. The United States Bureau of Standards (Fig. 13) was established at Washington in 1901.

Originally the Bureau was only a place for keeping the pound, yard, gallon, bushel, meter, kilogram, etc., up to standard, but it has grown to be much more than this. The many new industries that have arisen in recent years and the application of scientific methods to old industries make new standards necessary. It is also important that both the quantities of the materials that go into manufactured articles, as well as their qualities, or properties (cf. § 5), shall be definitely known. Hence the Bureau furnishes standards of measurement for electricity, the unit of light intensity (known as the "candle power";

cf. § 171), standard thermometers for determining temperature (cf. § 63), and standard pyrometers for determining higher temperatures than the thermometer will measure. We can realize the value of this work when we understand that the measurement of high temperatures, for example, is necessary in such important industries as making glass,

pottery, and illuminating gas, and in the preparation and working of the metals. Besides, the Bureau determines the strength of materials such as wood, steel, and cement, the fuel value of coal, petroleum, etc., as well as many other properties which the modern manufacturer needs to know.

16. Summary.- Science is organized knowledge. It arranges objects into groups or classes and studies the changes that objects undergo.

The scientific method is necessary in everyday life quite as much as in study and investigation.

Phenomena are the changes in objects.

Objects are portions of matter.

Matter exists in the solid, the liquid, and the gaseous form.

Matter occupies space and has weight.

Substances are the kinds of matter.

Properties are the qualities by which we distinguish one substance from another.

Space is that which contains no matter.

A space from which the matter has been removed is called à vacuum.
Matter has three dimensions: length, breadth, and thickness.
The meter is the unit of the metric system. It contains 39.37 inches.
The kilometer is 0.6214 miles.

The liter is the unit of volume. It equals 1 cubic decimeter, or 1.0567 U. S. liquid quarts.

The standard pound weight contains 16 ounces, or 7000 grains.

The gram is the weight of 1 cubic centimeter of pure water at 4° C. The kilogram is 1000 grams. It is the weight of one liter of pure water, and equals 2.2046 pounds.

The Bureau of Standards keeps the standard weights and measures, compares common weights and measures with the standard ones, makes new standards as new industries demand them, and determines the properties of materials.

17. Exercises.

1. Name the so-called "five senses." Are there any senses besides these? Explain.

2. Name two substances that you can distinguish from each other by each of the five senses. For "hearing," think of the way we test the genuineness of a coin.

3. Make a list of ten objects, and write opposite each the substance or substances of which it is made up.

4. Make a list of all the properties you can think of for each of the following substances: iron, water, sugar, wood, and coal.

5. Name five phenomena besides those of § 2.

6. Compare the way in which water is poured out of an inverted, small-mouth bottle with the way in which it is poured out of a pitcher. Explain.

7. Find the number of cubic feet of air in a room 14 ft. by 14 ft. by 9 ft. high. Find the weight of the air in ounces, if one cubic foot of air weighs 14 ounces. Reduce the weight to pounds.

8. Write down as grams and decimal parts of a gram 6 grams, 5 decigrams, 3 centigrams, and 9 milligrams. Subtract from this number the sum of 2 grams and 8 centigrams.

9. Locate the North Star to-night or the next clear night, note the hour, and draw a diagram to show the position of the "Big Dipper" with reference to the star. What stars of the dipper are the "Pointers"?

10. Look up (in the Glossary at the back of this book) the difference between planets and fixed stars. Name some of the planets. Name some fixed stars besides Polaris.

11. Look up the distance of the moon from the earth. What is the moon's diameter? The earth's?

12. Look in a dictionary for the origin of the words quart, gram, meter, vacuum, and substance.

13. What are the proofs that the earth is sphere-like and not flat? 14. Name some scientific methods or apparatus that have recently been brought into our homes. Into factories. Into stores. Name

some that are used on the farm. In navigation.